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(No Model.) 3 Sheets-Sheet 1.

' C. E. ALLEN. y

GIRUUIT FOR TELEPHONE APPARATUS.

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WWALL N. PEKRS. Pham-Milf, Vlnhmun. D. C.

(No Model.)

3 Sheets-Sheet 2.

C. E. ALLEN. CIRCUIT POR TELEPHONE APPARATUS.

Patented Dem-1.8, 188,3.

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3 Sheets-Sheet 3.

(No Model.)

C. E. ALLEN. CIRCUIT FOR TELEPHONE APPARATUS.

. Patented Dec. 18, 1888.

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UNITED STATES "PATENfr4 OFFICE,

CHARLES E. ALLEE, oE NORTH ADAMS, MASSACHUSETTS, ASSieNoR or ONE-HALE To IRA J. MEAGLEL on RINGEAMTON, NEW YORK.

CIRCUITv FOR TELEPHONE `APPARATUS.

'SPECIFICATION'forming part of Letters'latent No. 290,307, dated December 18, 1883.

Application filed' May, 1883. (No model.)

To all whom, it may concern.-

Be it known that I, CHARLES E. ALLEN. a citizen of the United States, residing at North Adams, in the county of Berkshire and State of Massachusetts, have invented certain new and useful Improvements in Circuits for Telephone Apparatus, of which the following is a specification, reference being had therein to the accompanying drawings.

My present invention is an improvement in circuits for electrical apparatus.

It consists, essentially, of a main-line circuit arranged with reference to central offices of an extended exchange system, which oflices have each several local circuits branching therefrom and returning thereto, in which are several subscribers"instruments, arranged in such a way that a circuit may be made up from ground of any one individual station, or any local in any central office of an exchange, to the ground of any desired individual station of any line in any of the central offices from parts of return portions of said locals and main line in which the telephones and transmitters of the stations may be thrown in for conversation, the leading portions (in which are the controlling-magnets of the signaling devices) being temporarily cut ofi" from their return portions, thereby relieving the circuit to be talked through of much resistance.

I have been for some time engaged in experimenting upon the present system of telephoning, and have succeeded in producing a telephone-exchange system consisting of an automatic central office and certain improvements in signal-boxes, so constructed and located with reference to a system of circuits that in their use any subscriber in the exchange can, by the manipulation of his signalbox, ring the bell of any othersubscriber and place himself in independent telephonic connection with him without the aid of any onev -at the central ofce, and without ringing the bells of other subscribers. .The system referred to is not limited in its results to a single exchange and the offices and subscribers associated therewith, but it is `calculated to' embrace two or more exchanges located upon a main-line circuit, so that an individual suband signal-boxes are to be placed, Ihave` omitted to show or describe said apparatus at this time; but, in order to illustrate the subj ect of the present claims, I have shown in my several diagrams the ordinary cross-bar-plug switch-boards and the ordinary switch-connections, and at each individual station I have represented the ordinary electric-vibrating bell and the well-known hand-switches and press-keys.

In my drawings, composed of three sheets, I show on each a switch-board, several individual stations, and their relation to the circuits which form the subject of this application. The several sheets, when connected as hereinafter described, are intended to fully illustrate the gist of the present application.

Referring to the drawings, we may under stand, for purposes of illustration', that the NVP 13. R are respectively W'ashington, Baltimore, and Philadelphia. At -the Washington central office is a heavy battery, A, for the mainline, one side of which is grounded, andthe circuit from the other side runs through relay c3, switch b5, bar 2, main-line wire out; thence to main-line wire on Sheet 2, through relay e, switch b, switch-bar 2b, main-line wire, and on to main line shown in Sheet 3; thence through relay c at I?. 7 central office, switch b, bar 2c, main-line return-Wire; thence to mainline return-Wire of Sheet 2, and thence to mainline return-wire of Sheet l, terminatitig on bar 3, leaving the main line normally open. Bar lL of the WJ switchboard is in connection with the earth through wire c, switch c, secondary of induction-coil in transmitter b, and

three exchanges represented by the capitals telephone 11. Bars 3" and 23C in the 13. and 1).7 centrals are in connection-with the return ofmainline bybranchesSS. Fromthe remaining perpendicular bars of cach central-oiiice switch-board local circuits extend, one each of which takes in several subscribers7 stations, and, returning, each of said circuits occupies two bars of the switch-board, as shown, the exit-wires being coimected to local batteries. rlhe wires not connected to batteries are the return-wires of the circuits. All of the local circuits are similar, and one of them, starting and terminating` with a central ofce, may be described as follows: One pole of battery A, which has its opposite pole grounded, runs through annunciator a, switch b, bar 4, to local-line wire E, which takes in switches c, relay-magnets m of station CL C), and then rcturns to central office 111.,7 terminating on bar 5, leaving said local circuit normally open. In its return the said local circuit passes through stations C) (3*, at either of which it may be `grounded through a branch circuit, f, by pressing the spring-key c, which is normally open, or through the secondary of transmitter T and telephone H by closing switch c2, which is also normally open. Rus a relay, the lever of which, when a current is through magnet on, closes the bell-circuit, in which battery A" is located, causing the bell 1 to ring. All the plugs of the switch-board, except that of bar l, are located, ready for use, in the lowest horizontal row of holes. Bar l is normally plugged at its intersection with its corresponding horizontal bar, l^. Now, let us suppose a subscriber-say C17 ofthe 1). exchange-wants a subscriber, C, ofthe 13. exchange. The subscriber at C1T first signals the central office 1). by pressing the key c at said station, which completes the circuit of battery AT, causing the tag of annunciator a to drop. 11e now opens switch c at his station to open the exit portion of the line L, closes the switch c, which completes the battery-circuit at C through the primary wire of the transmitter, then closes switch at to ground the return of circuit Ll through the secondary of the transmitter and telephone, and then puts his telephone to his ear. As soon as the tag of annunciator a drops, the operator at central office 1). opens switch bwand removes the pin in bar 5c to the next hole above, putting it in connection with horizontal and perpendicular bars 10" lc and to ground through the transmitter and telephone of said central ofce, thereby putting said transmitter and telephone in circuit with those of station C, through a portion of the return-circuit of L". The operator of central office 1). now says Hello to the individual at station )7, and thc latter responds, telling who he wants tocommunicate with. The operator at the central office 1). now removes the plug from bar 5c to next hole above and plugs it in connection with horizontal bar TX, and then opens switch c'L of central transmitter and rcmoves the plug from bar 3 to next hole above and plugs it in connection with horizontal bar l. The desired central office 13. is now signaled by pressing the key d of central office 1). 1t will be seen that by pressing this key the bells y of the several central offices will be caused to ring by giving ground to the return portions of main-line circuit, which completes the circuit ofthe main-line battery Athrough the bell-relays. Each central office has a certain signal ascribed to it-say, for instance, the signal for \V. is one ring, for 13.7 two rings, and 1). three rings. The operator at 1). gives the 13. signal by pressing his key the proper number of times. As soon as the operator ofthe B central officchears his signal, he opens his switch b to open the leading portion ofthe mainline circuit. He then removes the pin from the lower hole in upright'bar 3" to the next hole above, and plugs bar 3" into connection with bar 1W. The branch circuit of the return portion ofthe main lineis now in connection with the earth at central office 13.,7 through secondary of transmitter T and telephone l-l. As soon as the operator at the 13. signals 13, he (the 1). central-office operator) closes his switches c, opens his switch b", and plugs his bar in the manner j ust described for central office 13, and then the two central ofiices are in circuit with each other through their branch circuits and a portion of the return of main-line circuit. The operator at 1). now tells the operator at 13. to get C". 13. central ofiice operator now opens switch c, removes the plug in bar 3b one hole higher, and removes plug from bottom hole in bar 5 to the bar l"X and signals C by pushing key Z at the 13. central station the proper number of times to sound the C signal. Pushing this key d the proper number of times gives the proper signal for station Cl1 by giving ground to the return of said circuit. Cl1 now hearing his signal, opens switch c and closes the transmitter-switches c c2, and listens through his telephone. Hethen responds Hello to operator at the 13. central ofice, andthe latter informs him that he is wanted, and removes the plug in bar 5" to the hole above and plugs bar 5" in connection with the samehorizontal barf1J that he plugged bar 3 with. Subscribers or individuals at C and C1T are now in communication with each other, their circuits being as follows: From ground at C" station through the telephone and transmitter of said stationswitch c`l to return portion of local line. L4. The lead portion of this line having been opened by the opening of switch c, the circuit is necessarily through the return portion of bar 5 at central office 1). through a portion of horizontal bar 2CX into perpendicular bar 3", through branch S of 1). central office to return portion of main line; through this into branch S of 13, cent-ral office, perpendicular bar 3; through a portion of horizontal bar 2'JX into perpendicular bar 5; return of local circuit LL to station C through switch Cz of IOO IIO

C subscriber, his transmitter, and telephone to ground. It will thus be seen that all of the relays, signaling-magnets, and batteries are cut out of circuit while conversation is passing between two individual stations. By this arrangement the line is freed of much of the resistance which would tend otherwise to interfere with conversation between any two points of communication. A

Transmitters and telephones as represented may be arranged according to any of the usual methods, so as to be looped into the return portion of the main-line circuit for the purpose of interviewing parties who are connected to ascertain when they have finished talking, or for the purpose of giving instructions, &c.

It may be observed that the return portions of the local circuits, instead of returning through the several subscribers instruments, may be so run as to return direct to the central offices from which they started, and have branches extending from them to the several subscribers7 instruments, and ground may be given to the return at any station by grounding the branch either through the press-key or through the telephone and transmitter.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is- Y 1. A battery or generator, with one of its poles grounded and the circuit from the other formi-ng a loop, (not grounded,) upon which is situated several stations, each with its signaling or controlling magnets situatedin the leading portion of the loop, and provided with suitable means for opening and closing said portion of loop-circuit, and with suitable devices for giving ground to the return portions of the loop, either directly or through cornmunicating-instruments, as and for the purpose set forth.

2. One or more generators and main line loop-circuits arranged as described, their stations being central offices, at each of which are situated several other generators with loopcircuits and stations extending therefrom, and means at each central office and station by which a circuit may be made up from parts of return portions of the main-line loop-circuit and any of the local loop-circuits, substantially as set forth.

In testimony whereof I affix my signature in presence of two witnesses.

cHARLEs E. ALLEN.

Vitnesses W. W. HoLLINGswoRTH, JQHN W. DONN. 

